From the Polish Patent 167519 a method is well-known to produce a soluble cellulose by a direct treatment of cellulose pulp with enzymes type cellulases derived from the fermentation of the Aspergillus niger IBT fungi with following characteristic: CMC activity-0.1-15 U/cm3 ; FPA activity 0.01-1.0 U/cm3 ; 3- glucoside activity 0.1-15.0 U/cm3 and proportion of CMC to FPA activity in the 1-100 range. The enzymatically treated cellulose shows a dissolving ability in hydroxides of alkali metals.

From the Polish Patent 167776 a method is well-known to produce fibres, film and other products from soluble cellulose. The soluble cellulose obtained by enzymatic treatment with cellulases from Aspergillus niger IBT having following characteristics: average polymerisation degree DPW at least 100, water retention value WRV in the 50-100% range, energy of hydrogen bonds EH below 16 kJ/mol is mixed at-10°C to 10°C with an aqueous solution of alkali metal hydroxides with concentration 5-15% during 15-2880 minutes to achieve a homogeneous solution of cellulose. The alkaline solution of cellulose is filtered and deaerated and subjected to coagulation in an acidic bath consisting of an inorganic or/and organic acid solution. The obtained product is washed with water to attain a neutral reaction and is possibly dried.

From the German Patent DE 19624867 a method is also well-known to produce cellulose pulps with improved solubility in aqueous solutions of N, N- methylmorpholine oxide. The aqueous suspension of cellulose pulp is at first treated with cellulases and/or xylanases with activity at least 0.01 U/cm3 at temperatures 20 to 60°C and pH 3.5 to 7.0. The cellulases were derived from Aspergillus niger while the xylanase from Trichoderma viride fungi.

From the German Patent DE 19624866 a method is well-known for the manufacture of cellulose pulp with improved activity for the production of cellulose acetate. An aqueous solution is enzymatically treated with cellulases from Aspergillus niger and/or xylanases from Trichoderma viride with enzyme activity at least 0.01 U/cm3 at temperature 20-60°C and pH 3.5-7.0.

The solubility of cellulose made according to well-lçnown methods is usually in the 70-90% range and its solutions show poor stability, low a-cellulose concentration and, at the same time, very high viscosity. The solutions are stable usually at temperatures below 0°C, while the manufactured products like fibres or film have poor mechanical properties. Manufacturing procedures are difficult which results from the properties of the spinning solution like high viscosity, low temperature, poor stability and filterability.

The method for the manufacture of fibres, film and other products, according to this invention, consists in a mechanical and/or enzymatic pretreatment of the starting cellulose pulp in form of an aqueous dispersion in a buffer with pH not lower than 2.5, possibly containing enzymes like xylanases or cellulases. Next, after a possible removal of the water or solution surplus, the pretreated cellulose pulp is subjected to an enzymatic treatment by means of enzyme complex containing cellulases preferably from Aspergillus niger or Trichoderma reesei with endo-l, 4-B-glucanase activity not less than 0.1 U/cm3, preferably 1.0-3.0 U/cm3, B-glucosidase activity not lower than 0.01 U/cm3, preferably 0.05-0.1 U/cm3, FPA activity not lower than 0.01 U/cm3, preferably 0.1 to 1. 0 U/cm3 and/or xylanase, preferably from fungi Trichoderma reesei, with endo-1, 4-ß- xylanase activity not lower then 0.5 U/cm3, preferably 30-100 U/cm3. Surplus of the enzyme-containing solution is next removed and the enzymes remaining in the pulp are deactivated by water-washing at temperature above 60°C. The obtained modified cellulose pulp is characterized by DPw not lower than 200, WRV not lower than 50%, preferably 70-120%, EH not higher than 20 kJ/mol, preferably 10-15 kJ/mol, polydispersity degree Pd not lower than 2, and water content not lower than 5%, preferably 20-70%. The pulp is then dissolved in an aqueous solution of alkali metals, preferably in sodium hydroxide with 5% concentration, temperature not lower than 0°C, preferably 0-3°C, during at least 1 minute, preferably 10-60 minutes. The alkaline solution of cellulose is next filtered and deaerated and afterwards subjected to coagulation in water or aqueous solution of acid, preferably sulphuric acid. The product is thereafter washed out with water to a neutral reaction and optionally dried.

The method according to the invention includes also the pretreatment of cellulose pulp by swelling in water or in an aqueous buffer with pH 2.5 to 6.0 and/or in a solution of cellulases and/or xylanases, preferably from Aspergillus niger or Trichoderma reesei, with endo-1, 4-ß-glucanase activity not lower than 0.05 U/cm3 and endo-1, 4-p-xylanase activity not lower than 0.1 U/cm3 during 1-1440 minutes at temperature 10-60°C preferably 20-40°C. After the removal of water or solution surplus, the cellulose pulp undergoes a mechanical treatment at 20-40°C during 1-360 minutes.

The enzymatic treatment of cellulose pulp, according to the invention, is preferably accomplished in a suspension of an enzymatic complex with the cellulose concentration no lower than 0.1%, preferably 5-10% with continuous stirring and/or continuous recirculation of the enzyme liquor at temperature not lower than 10°C, preferably 20-50°C, during at least 1 minute, preferably 50- 360 min., at pH not higher than 7, preferably 4-6.

The surplus of the enzymatic complex after the enzymatic treatment can be accordingly to the invention, recirculated to the process with supplement of fresh enzyme to keep the activity constant.

The aqueous solution of alkali metal hydroxides can contain the addition of zinc oxide not lower than 0.01%, preferably 0.1-0.9%, and/or urea not lower than 0.1%, preferably 1-4% wt.

According to the invention, the cellulose pulp is dissolved in aqueous solutions of alkali metals, preferably with vigorous agitation with a speed not lower than 100 rpm and temperature increasing up to 5-12°C at the end of dissolving.

During the coagulation of fibres and film, according to the invention, an extension is applied not lower than 10%, preferably 40-100%.

The method according to the invention is environment-friendly as the cellulose is enzymatically processed and the products such as sausage casings, beads or fibrids are formed from an alkali-soluble cellulose. The attenuation of hydrogen bonds in the enzymatically modified cellulose makes the hydroxyl groups in the cellulose prone to solvatation resulting primarily from the weakening and/or destruction of the intramolecular bonds followed by intermolecular bonds. As a result of such processes stable alkaline cellulose solutions are originated. An advantage of the process is a controlled activation and degradation of cellulose caused by the action of cellulase and/or xylanase leading to a modified, alkali-soluble cellulose pulp with an assumed molecular, supermolecular and morphological structure.

Owing to the applied mechanical and/or enzymatic treatment which causes swelling of the cellulose and eases the diffusion of enzymes into the capillary system as well as the applied enzymatic treatment with cellulases and/or xylanases, the modified cellulose is characterized by solubility in alkalies exceeding 95% usually reaching 98-100%. The alkaline solutions are stable at temperatures beyond 0°C and are characterized by high a-cellulose content and viscosity which allows processing. Urea and zinc oxide are applied for the improvement of stability and quality of the solutions.

An advantage of the method is the possibility to recirculate the enzyme solution after the enzymatic treatment of cellulose, thus contributing to better process economy.

The temperature-programmed dissolving of the modified cellulose in alkaline solutions has an evident impact on the quality of the solutions and the properties of obtained products. The forming of fibres, film and other products is accomplished by the coagulation of the alkaline cellulose solution in an acidic bath with simultaneous neutralizing the alkalies contained in the solution. The applied extension, in the case of fibres, film or casings, confers better orientation and improves the structure of the products which leads to better physical- mechanical properties.

The method, according to the invention, is much simplier and safer than well- lcnown methods while the obtained products demonstrate better properties than well-known cellulosic products.

The method according to the invention, is illustrated with following examples not limiting the scope of the invention.

Example 1.

100 wt parts of a beach wood pulp in sheets was used with following properties: moisture content of 6%, DPw=657, WRV=61. 6%, a-cellulose content of 94.4%, crystallinity index CrI=68. 0%, EH=17. 4-24.2 kJ/mol. The pulp was swollen in 800 wt parts of water at 20°C during 30 minutes. Next 718 wt parts of the water was removed by pressing and the pulp was shredded in a Werner- Pfleiderer mill at 20°C during 60 minutes. The ground pulp was dried at 20°C.

The pretreated cellulose was introduced to the reactor with agitator.

1900 wt parts of a cellulose solution in an acetate buffer with pH=4.8 are added.

The cellulases were derived from Trichoderma reesei fungi, characterized by endo-1, 4-ß-glucanase activityof2. 5U/cm3 filtration paper activity FPA of 0.15 U/cm3, p-glucosidase activity of 0.08 U/cm3, while the concentration of the cellulose in the suspension was 5 wt %. The enzymatic treatment lasted 180 minutes at 50°C and pH=4.8. The obtained suspension of modified cellulose was filtred, washed with water at 90°C to complete deactivation of the remaining enzyme, followed by several washings with water at 20°C to fully purify the cellulose. The modified cellulose pulp was dried at 30°C to constant weight.

93.8 wt parts of white biotransformed cellulose were obtained with following characteristic: moisture content of 5%, average polymerization degree DPW= 398, water retention value WRV=81. 0%, crystallinity index CrI=70. 5%, energy of hydrogen bonds EH=12. 8-14. 5 1cJ/mol and solubility degree in 9% solution of sodium hydroxide Sa-99%. To 30 wt parts of such modified cellulose pulp 100 wt parts of water were added and the mixture was cooled down to 1°C and dissolved in 470 wt parts of an aqueous solution of sodium hydroxide with 10.2% concentration containing 30 wt parts of urea and 5.3 wt parts of ZnO at 0°C. The dissolving lasted 30 min with the agitator at 900 rpm. An alkaline cellulose solution was obtained at 8°C, containing 4.99% of a-cellulose and 8.15% wt sodium hydroxide. The solution had following properties: viscosity at 8°C of 100 seconds, clogging value Kw*=131, stability at 15°C=48 hours. The solution was filtered and deaerated during 10 hours at 15°C. From the solution a cellulosic film was formed in lab-scale at 25°C whereby as coagulation bath a 12% solution of sulphuric acid was used.

30.9 wt parts of a cellulose film were obtained. The film was 0.028 mm thick with breaking tension 40.0 MPa, elongation at break 5.3% and 8% moisture content.

Example 2.

100 wt parts of cellulose with properties as in Example I were shredded as in Example I. Next 182 wt parts of wet cellulose pulp were introduced to a reactor equipped with an agitator and subjected to the action of 1818 wt parts of a cellulases solution in a buffer (pH=4. 8). The cellulases were derived fom the Trichoderma reesei fungi and was characterized by: endo-1, 4-ß-glucanase activity of 2.5 U/cm3, filtration paper activity FPA of 0.15 U/cm3, p-glucosidase activity of 0.08 U/cm3. The cellulose concentration in the suspension was 5%.

The enzymatic treatment lasted 180 minutes at 50°C and pH=4.8. The obtained cellulose suspension was filtered, washed with water at 90°C to complete deactivation of the remaining enzyme and afterwards washed several times with 20°C water to obtain a pure product. 93.8 wt parts of white, modified cellulose pulp were obtained, characterized by: moisture content 5%, DPW=398, WRV= 81.0%, CrI=70. 5%, EH=12. 8-14.5kJ/mol and Sa-99%. To 49 wt parts of modified cellulose pulp containing 71.5% of water, 16 parts of water were introduced and cooled down to 0°C. Such prepared pulp was dissolved in 235 wt parts of aqueous sodium hydroxide with 10.2% concentration, containing 15 wt parts of urea and 2.65 wt parts of ZnO at 0°C. The dissolving time was 30 minutes with agitation speed 1000 rpm. An alkaline cellulose solution was obtained at 7°C, containing 4.47% of a-cellulose and 7.28% of sodium hydroxide characterized by: viscosity at 8°C of 77 seconds, Kw*=156, stability at 15°C of 48 hours. The solution was deaerated during 10 hours at 15°C whereafter cellulose beads were formed from the solution using a spinneret with 100 capillaries with 1 mm diameter. A solution containing 15% sulphuric acid and 5% sodium sulphate at 20°C was used as coagulation bath. The formed beads were several times washed with water.

49.6 wt parts of beads were produced with 70% water content and WRV=876%.

Example 3.

100 wt parts of cellulose with properties as in Example I were first 30 minutes swollen in 800 wt parts of an acetate buffer (pH=4.8). The surplus of the buffer was next squeezed out and the pulp was shredded in an Werner-Pfleiderer mill at 20°C during 60 minutes and afterwards dried at 20°C. The pretreated cellulose was introduced to a reactor with agitator and subjected to the action of 1329 wt parts of a mixed solution of a xylanases from the Trichoderma reesei strain with endo-1, 4-ß-xylanase activity at 69.7 U/cm3 and a cellulase from Trichoderma reesei with endo-1, 4-p-glucanase activity at 2.5 U/cm3 in the 3: 1 proportion in a pH=4.8 acetate buffer. The concentration of cellulose in the suspension was 7%. The enzymatic treatment lasted 2 hours at 50°C and pH=4. 8. The obtained cellulose suspension was washed as in Example I. 98 wt parts of white modified cellulose were obtained with 7% moisture content, DPW=436, WRV=84. 0%, CrI=71. 2%, EH=1 1. 6-15.2 1,-mol and Sa=96%. To 30 wt parts of such cellulose with 5% moisture, 100 parts of water were added and cooled down to 1°C. The cellulose pulp was next dissolved at 0°C in 470 wt parts of a 10.2% aqueous sodium hydroxide, containing 30 wt parts of urea and 5.3 wt parts of ZnO. The dissolving time was 30 minutes with agitation speed 1000 rpm. An alkaline cellulose solution was obtained at 6.0°C, containing 4.81% of a-cellulose and 8.02% of sodium hydroxide characterized by: viscosity at 8°C of 540 seconds, Kw*=159, and stability at 15°C of 24 hours. The solution was filtered and 15 hours deaerated at 15°C, whereafter a cellulose film was formed in lab-scale from the solution at 25°C whereby a 12% aqueous sodium of sulphuric acid was used as coagulation bath.

2.99 wt parts of cellulosic film were obtained with 8% moisture content characterized by: 0.035 mm thickness and breaking tension of 50.7 MPa and elongation at break 4. 4%.

Example 4.

100 wt parts of cellulose with properties as in Example I were first swollen during 1440 minutes in 800 wt parts of an acetate buffer (pH=4.8). Next after out-squeezing of the surplus of the buffer the cellulose pulp was shredded in a Werner-Pfleiderer mill during 60 minutes at 20°C. The pretreated pulp was dried at 20°C. The obtained cellulose pulp in the quantity of 100 wt parts was placed in a reactor equipped with agitator and subjected to the action of 1567 wt parts of a mixture composed of the xylanase from the Trichoderma reesei strain with endo-1, 4-p-xylanase activity at 69.7 U/cm3 and cellulases from the Trichoderma reeser strain with endo-1, 4- (3-glucanase activity at 2.5 U/cm3 in the 3: 1 propartion in an acetate buffer (pH= 4.8) with the 6% concentration of cellulose in the suspension. The time of the enzymatic treatment was 360 minutes at 50°C and pH=4.8. The obtained suspension of cellulose was purified as in Example I. 95.2 wt parts of white modified cellulose pulp were obtained with following characteristic : moisture content of 7%, DPw=405, WRV=78.0%, CrI=69. 8%, EH=12. 4-13.9 kJ/mol and Sa-98%. To 24 wt parts of the modified cellulose pulp with moisture 5%, 100 parts of water were added and cooled down to 1°C. The pulp was dissolved in 476 wt parts of a 10.2% aqueous sodium hydroxide, containing 30 wt parts of urea and 5. 3 wt parts of ZnO at 0°C. The dissolving time was 30 minutes with agitating speed 900 rpm. An alkaline solution of cellulose was obtained at 6.5°C, containing 3.83% of a-cellulose and 7.84% of sodium hydroxide characterized by viscosity at 8°C of 38 seconds, Kw*=159, and stability at 15°C of 48 hours. The solution was filtered and 10 hours deaerated at 15°C. From the solution a film was formed at 25°C in lab-scale whereby an aqueous 12% solution of sulphuric acid was used as coagulation bath.

25.8 wt parts of cellulosic film were obtained with 8% moisture content with following properties: thickness of 0.022 mm, breaking tension 60.3 MPa and elongation at break 7.1%.

Example 5.

100 wt parts of cellulose with properties as in Example I was swollen during 30 minutes in 800 wt parts of a solution of xylanases from the Trichoderma reesei with activity endo-1, 4-p-xylanase 69.7 U/cm3 in an acetate buffer at pH=4.8.

After out-squeezing the enzyme solution, the cellulose was shredded in a Werner Pfleiderer mill at 20°C during 60 minutes. The cellulose pulp after the mechanical treatment was dried at 20°C. The pretreated cellulose pulp was placed in a reactor with agitator were it was subjected to the action of 1900 wt parts of a solution of cellulases from Aspergillus niger with activity endo-1, 4-0- glucanase equal to 1.9 U/cm3. The concentration of cellulose in the solution was 5%. The cellulose was 60 minutes enzyme-treated at 50°C and pH=4.8. The obtained cellulose suspension was washed as in Example I. 95.2 wt parts of white biotransformed cellulose were obtained with following characteristic: moisture content of 5%, DPW=435, CrI=72. 6% EH=13. 5-17.5 kJ/mol, VVRV=81. 5% and Sa-96%. To 30 wt parts of dried, biotransformed cellulose pulp with 5.0% moisture, 100 parts of water were introduced and the mix was quenched to 0°C. The cellulose pulp was dissolved in 470 wt parts of a 10.2% water solution of sodium hydroxide containing 30 wt parts of urea and 5. 3 wt parts of ZnO at 0°C. The dissolving time was 30 minutes. An alkaline cellulose solution was obtained at 6°C, containing 4.71% of a-cellulose and 7.94% sodium hydroxide with viscosity of 268 sec at 8°C, clogging value Kw*=145, and 48 hours stability at 15°C. After 10 hours of deareating at 15°C, a film was formed from the solution at 25°C in a coagulation bath containing an aqueous 12% solution of sulphuric acid.

30.1 wt parts of cellulosic film, was obtained with following properties: moisture content of 8%, thickness 0.023 mm, breaking tension of 43.9 MPa and elongation at break 4.3%.

Example 6.

100 wt parts of spruce cellulose in sheets with following characteristic: moisture content of 5%, DPw 577, WRV=65%, a-cellulose content of 94.0%, CrI=69. 0%, EH=18. 3-21.4 kJ/mol were shredded in a Werner-Pfleiderer mill as in Example I. The obtained cellulose pulp was placed in a reactor with agitator and treated with 1900 wt parts of a solution of cellulases from the Aspergillus niger strain with endo-l, 4-ß-glucanase activity of 1.9 U/cm3 with 5% concentration of cellulose in the suspension. The enzymatic treatment time was 180 minutes at 50°C and pH=4. 8. The obtained cellulose suspension was purified as in Example 1. 97.1 wt parts of the biotransformated white cellulose pulp were obtained characterized by: 6% of moisture content, DPW=387, WRV=81.0%, CrI=70. 2%, EH=12. 7-14.5 kJ/mol and Sa=98%. To 33 wt parts of the biotransformed cellulose with 6% moisture, 97 parts of water were added and cooled down to 1°C. The pulp was next dissolved in 470 wt parts of a 10.2% of aqueous sodium hydroxide, containing 30 wt parts of urea and 5.3 wt parts of ZnO at 0°C. The dissolving time was 30 minutes at agitating speed 120 rpm. An alkaline solution was obtained with temperature of 6.5°C, containing 5.2% of a-cellulose and 8.57% of sodium hydroxide characterized by: viscosity at 8°C of 221 seconds, Kw*=147, and stability at 15°C of 48 hours. The solution was filtered and 10 hours deaerated at 15°C, whereafter a cellulosic film was formed from the solution in lab-scale at 25°C. A 12% sulphuric acid solution was used as coagulation bath.

32.8 wt parts of cellulosic film were obtained characterized by: thickness of 0.021 mm, breaking tension 42.1 MPa and elongation at break 5.5%.

Example 7.

100 wt parts of cellulose with properties as in Example I were shredded in a Werner-Pfleiderer mill as in Example I. The obtained cellulose pulp was placed in a reactor with agitator and subjected to the action of 1150 wt parts of a 3: 1 mixture of xylanases from the Trichoderma reesei strain with endo-1, 4- (3- xylanase activity of 69.7 U/cm3 and cellulases from Aspergillus niger strain with endo-1, 4-p-glucanase activity of 2.4 U/cm3 in an acetate buffer (pH=4.8). The enzymatic treatment time was 120 minutes at 50°C and pH=4.8. The obtained cellulose suspension was purified as in Example I. 96.2 wt parts of white biotransformated cellulose pulp with 7.0% moisture were obtained with following characteristic: DPw=469, WRV=86. 4%, CrI=71. 3%, EH=12. 2- 16.7 kJ/mol and Sa-96%. To 30 wt parts of the biotransformed cellulose pulp with 5% moisture, 100 parts of water were introduced and cooled down to 1°C.

The cellulose pulp was dissolved in 470 wt parts of an 10.2% aqueous sodium hydroxide, containing 30 wt parts of urea and 5.3 wt parts of ZnO. The dissolving lasted 30 minutes with agitating speed 900 rpm. An alkaline cellulose solution was obtained at 6.5°C, containing 4.8% of a-cellulose and 8.16 % sodium hydroxide with following characteristic: viscosity at 8°C of 1280 seconds, Kw*=110, and stability at 15°C of 48 hours. The solution was filtered and 10 hours deaerated at 15°C, whereafter a cellulosic film was formed from the solution at 25°C in lab-scale. A 12% water solution of sulphuric acid was used as coagulation bath.

30.1 wt parts of cellulosic film with 8% moisture were obtained with following characteristic: thickness of 0.031 mm, breaking tension 43.5 MPa and elongation at break 3.5%.

Example 8.

100 wt parts of an alkaline solution of the pulp modified as in Example VI were used for spinning of fibres with take-up speed 20 m/minute in a spinning bath containing 12% sulphuric acid and 4.4% sodium sulphate. A spinneret with 1000 holes each 0.065 mm in diameter was used for the spinning. The obtained continuous fibres were purified in a water bath; a spin-finish was applied on the fibres. The fibres were dried at 50°C eventually.

59.1 wt parts of cellulosic fibres were obtained with following properties: moisture content of 12%, titre of 3.42 dtex, tenacity 12.6 cN/tex and elongation 14.5 %.

Example 9.

100 wt parts of the alkaline cellulose solution as in Example VI was diluted in the proportion 1 : 3 and used for the manufacture of cellulosic beads.

A spinneret with 100 capillaries each 1 mm in diameter was used for the forming of beads at 25°C in a 12% aqueous solution of sulphuric acid. The beads were afterwards washed with water.

74.0 wt parts of wet beads were received. The beads contained 7% of cellulose, were 4-5 mm in diameter and had WRV=856%.

Example 10.

100 wt parts of the alkaline cellulose solution as in Example IV was used for the manufacture of cellulosic fibrids using a device with 100 holes spinneret with 0.09 mm diameter. The fibrids were formed in temperature of 35°C in 12% aqueous sulphuric acid and washed with water afterwards.

65 wt parts of fibrids were obtained with a diameter of 10 urn, length of 500 um, containing 7% of moisture and with the WRV equal to 321%.